The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

THE USE OF DEADSPACE TO TIDAL VOLUME RATIO (VD/VT) IN PREDICTING EXTUBATION SUCCESS IN A PEDIATRIC CRITICAL CARE SETTING

D. Hamel1, D. Craig2, S. Srinvasan3, I. Cheifetz4


Background: The deleterious effects of failed extubation as well as prolonged mechanical ventilation have been widely reported. It is for these reasons that an objective assessment of extubation readiness is essential. It has been previously reported that Vd/Vt <0.5 during a pressure support trial was predictive of extubation success.[1] However, it has not been determined if Vd/Vt < 0.5 is predictive of extubation success in pediatric patients in which mechanical ventilation is clinically determined, rather than controlled by a study protocol.
Hypothesis: Vd/Vt < 0.5 obtained during routine mechanical ventilation would be predictive of extubation success for pediatric patients.

Methods: A heterogeneous group of 53 mechanically ventilated patients (40.6 ± 63.7 months; 14.0 ± 18.7 kg) receiving continuous volumetric capnography monitoring (NICO2; Monitor; Respironics, Inc.; Wallingsford, CT) were studied. Inclusion criteria required an anticipated length of ventilation > 24 hrs and a functioning indwelling arterial line. Vd/Vt was calculated within a six hour period prior to extubation for each patient. Ventilator parameters were at the clinician’s discretion and not adjusted for this study. The decision to extubate was based on standard clinical practice. Only the first extubation attempt per patient was included. Data were compared with Chi-square analysis.

Results: There were 36 successful extubations. Vd/Vt was </= 0.5 for 33/36 (92%) of the successful extubations and for only 4/17 (24%) of the failed extubations. The association between Vd/Vt and extubation success was statistically significant with a Chi-square value of 25.4 (p < 0.0001). The Odds Ratio of successful extubation is 4.75 for someone in the Vd/Vt </= 0.5 group. Logistic regression indicated a statistically significant association between Vd/Vt and the probability of successful extubation (p < 0.002).

Conclusion: Vd/Vt provides clinicians with valuable data in determining the probability of extubation success from a pulmonary standpoint. Serial measurements of Vd/Vt may help clinicians to shorten length of ventilation while minimizing the risk of extubation failure.


[1] Hubble CL, Gentile MA, Tripp DS, Craid DM, Meliones JN, Cheifetz IM. Deadspace to tidal volume ratio predicts successful extubation in infants and children. Crit Care Med 2000;28(6):2034-2040.

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